A number of processes in petroleum production and refining, coal conversion and the chemicals industry produce as by-products liquid hydrocarbons containing insoluble solid particles oftentimes in the form of finely divided suspended inorganic solids.
Among the processes which produce liquid hydrocarbons containing appreciable amounts of finely divided suspended solids are steam cracking, catalytic cracking, coal gasification, coke production, and liquification of coal. Steam cracking produces a steam cracking tar which contains insoluble particles of coke generally at a level of 0.001 to 5.25% with the remainder being useful heavy liquid hydrocarbons. Catalytic cracking produces cat cracker bottoms which contain catalyst fines generally at a level of 0.1 to 5 wt.% with the remainder being useful heavy liquid hydrocarbons. Liquefication of coal, such as by the donor solvent technique as described in U.S. Pat. Nos. 4,085,031; 4,253,937; 4,048,054 and 4,045,328, produces a solvent-coal slurry containing insoluble particles. Other liquids from coal are produced in its conversion processes by, for example, in its gasification, coke preparation and other processes involving the pyrolysis of coal. These liquid hydrocarbon streams contain insoluble particles which are desirably removed or reduced in level to allow for their use as a fuel oil or as a feedstock for producing other products.
These liquid hydrocarbon streams oftentimes are routed to a settling tank wherein the solid particles (catalyst fines, coke, inorganic matter, are allowed to gravity settle over an extended period of time whereby an upper layer of substantially particle-free liquid hydrocarbons can be decanted off for product use. Settling of the particles may also be provided for in intermediate or shipping tanks. Unfortunately gravity settling is too slow for the refinery, coal conversion and chemical processes now in use.
Improved techniques which are in use include electrofiltration, filtration and centrifugal separation. The latter two approaches appear to have a low capacity or throughput and a high capital cost. Electrofiltration was handicapped by lack of a regenerable filter media which is stated to have been overcome by the use of hard, smooth spherical glass beads as taught in U.S. Pat. Nos. 3,799,855 and 3,799,856. Unfortunately these techniques are further limited since the typical oil-suspendible solids have average diameters of size below about 100 microns (commonly described in the art as difficultly filterable solids) which size makes satisfactory separation by mechanical separation techniques, including filtration, centrifugation and settling difficult to impossible.
Chemical treatments for oil containing suspended solids have been proposed in the art but, in general, each method suffers from some disadvantage as seen from the prior art discussion of U.S. Pat. No. 4,094,770 wherein the patentee has taught a process for separation suspended unfilterable pacticulate solids from an oil by agglomerating the solids by means of an agglomerating agent comprising a mixture of acetone and 2-butanone.
In U.S. Pat. No. 4,029,567 an agglomerating agent, especially ethanolamine is used to help separate the mineral solids and undissolved coal particles from a solution of coal liquification products.
Gravity settling can also be enhanced by the presence of a surface-active agent as taught in U.S. Pat. No. 2,952,620 wherein solid particles of a silica-alumina cracking catalyst suspended in a heavy gas oil was separated from the oil by treating the suspension with an aqueous solution of a nonionic surface-active agent e.g. a condensation product of diisobutyl phenol and 9-10 moles of ethylene oxide.
Gravity settling can be induced by use of a settling vessel in which the hydrocarbon oil containing the solids is subjected to a temperature gradient (see U.S. Pat. No. 4,048,063).
The dedusting of solids-containing hydrocarbon oils such as these derived from oil shale is accomplished by the use of various surface active agents (see U.S. Pat. No. 4,407,707).
The use of gravity settling additives and techniques have enhanced the settling rate whereby gravity settling became a feasible method for removal of suspended solids requiring little additional capital investment, a mechanically simple operation and readily modified by change of the additive.
It is the object of this invention to enhance the gravity settling rate of suspended solids from hydrocarbon oils by use of an improved agglomeration aid alone or in combination with other additives.